Sustainable Energy – without the hot air

David MacKay, professor of Physics at Cambridge, has recently published a
wide ranging book on Sustainable Energy. He brings this huge subject down to size by
measuring our use and sources of energy in understandable units on a human
scale: kWh per day per person. He examines our uses of energy, and sources of
energy and concludes that 90% of current energy used in the UK derives from
fossil fuels and that this is clearly unsustainable.

He examines what sources of renewable energy are available and what quantity
we could reasonably achieve from solar energy, wind power, wave power etc. and
comes to some interesting conclusions about the scale of the problem and the practicalities involved.

The technical section provides well researched supporting detail and explanations.

David MacKay communicates his enthusiasm and takes you through some of
his discoveries. He ends his chapter on Smarter Heating as follows:

"My conclusion: can we reduce the energy we consume for heating?
Yes. Can we get off fossil fuels at the same time? Yes. Not forgetting
the low-hanging fruit – building-insulation and thermostat adjustments
– we should replace all our fossil-fuel heaters with electric-powered heat
pumps; we can reduce the energy required to 25% of today’s levels. Of
course this plan for electrification would require more electricity. But even
if the extra electricity came from gas-fired power stations, that would still
be a much better way to get heating than what we do today, simply setting
fire to the gas. Heat pumps are future-proof, allowing us to heat buildings
efficiently with electricity from any source.

Nay-sayers object that the coefficient of performance of air-source heat
pumps is lousy – just 2 or 3. But their information is out of date. If
we are careful to buy top-of-the-line heat pumps, we can do much better.
The Japanese government legislated a decade-long efficiency drive that has
greatly improved the performance of air-conditioners; thanks to this drive,
there are now air-source heat pumps with a coefficient of performance of
4.9; these heat pumps can make hot water as well as hot air.

Another objection to heat pumps is “oh, we can’t approve of people
fitting efficient air-source heaters, because they might use them for air-conditioning
in the summer.” Come on – I hate gratuitous air-conditioning
as much as anyone, but these heat pumps are four times more efficient
than any other winter heating method! Show me a better choice. Wood
pellets? Sure, a few wood-scavengers can burn wood. But there is not
enough wood for everyone to do so. For forest-dwellers, there’s wood. For
everyone else, there’s heat pumps."

His five energy plans for Britain all share a conclusion: use heat pumps

Having examined and quantified all the forms of practical sustainable energy
Professor MacKay proposes five possible energy plans for Britain:

one for those want to see diversity of supply from within Britain

one for the Greens (no nuclear, no coal)

one for those who don't like
industrialising the British countryside (no wind farms, no nuclear)

one for those who see nuclear as the solution and finally

one for those who wish to see the most economic result from the market after
a strong carbon tax

One notable conclusion is that the largest renewable
energy source he proposes consistently across all five options is from heat pumps.

The Professor has done the sums – and drawn his conclusions.
If you take time to read his book you are likely to come to similar conclusions.

Other nuggets from the Professor:

Turning phone chargers off when they are not in use is a
feeble gesture, like bailing the Titanic with a teaspoon.

In contrast, turning the thermostat down (or the air-conditioning
in hot climates) is the single most effective energy-saving technology
available to a typical person. Every degree you turn it down will reduce
your heating costs by 10%; and heating is likely to be the biggest form
of energy consumption in most buildings in Britain.

Small-scale combined heat and power is another looming
mistake. Yes, combined heat and power (that is, putting individual power
stations in each building, generating local electricity and heat to keep
the buildings warm) can be a slightly more efficient way of using fossil
fuels than the standard way (namely, centralised power stations and local
condensing boilers). But these CHP systems are only about 7% more
efficient. And they use natural gas, which is a fossil fuel!

The good news is, there is a much better way to generate
local heat: use heat pumps.

Roof-mounted micro-wind turbines are an utter waste of
resources. They never pay for themselves. A "600 W" micro-turbine
mounted on a typical roof in England generates only 0.04 kWh per
day – only one twentieth of the power of a lightbulb.

In contrast, roof-mounted solar water heaters are a no-brainer.
They really work: even where the sunniness is only about 30%, a modest 3-square-metre panel
can supply half of a typical family's hot water: about 3.8 kWh per day, on average.

Conclusions

David MacKay discusses the options and quantifies the alternatives
to allow you to come to your own conclusions, partly because some of
the choices are emotional and subjective.

However, some of his conclusions are crystal clear: he gives strong
support to solar heat capture
and use of heat pumps
– both well-established
technologies. He discusses seasonal fluctuations in renewables and comes
to the conclusion that “A useful technology will surely be
long-term thermal storage.”

Chief Scientific Advisor

Since writing his book David MacKay has been appointed as Chief
Scientific Advisor to The Department of Energy and Climate Change (DECC).

The new chief scientific advisor’s role is defined as,
"ensuring that the Department’s policies and operations,
and its contributions to wider Government issues, are underpinned
by the best science and engineering advice available".

On being questioned on his new role as Chief Scientific Advisor
David MacKay said:

“Climate change and secure
energy are two of the most urgent issues facing the UK and the global
community. The solutions must be rooted firmly in the science and I look
forward to advising the Government on how it can help deliver these important goals.”